refactor(webui): redesign Burn tab and fix gpu-burn memory defaults

- Burn tab: replace 6 flat cards with 3 grouped cards (GPU Stress,
  Compute Stress, Platform Thermal Cycling) + global Burn Profile
- Run All button at top enqueues all enabled tests across all cards
- GPU Stress: tool checkboxes enabled/disabled via new /api/gpu/tools
  endpoint based on driver status (/dev/nvidia0, /dev/kfd)
- Compute Stress: checkboxes for cpu/memory-stress/stressapptest
- Platform Thermal Cycling: component checkboxes (cpu/nvidia/amd)
  with platform_components param wired through to PlatformStressOptions
- bee-gpu-burn: default size-mb changed from 64 to 0 (auto); script
  now queries nvidia-smi memory.total per GPU and uses 95% of it
- platform_stress: removed hardcoded --size-mb 64; respects Components
  field to selectively run CPU and/or GPU load goroutines

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/overlay/usr/local/bin/bee-gpu-burn

@@ -2,7 +2,7 @@
 set -eu
 
 SECONDS=5
-SIZE_MB=64
+SIZE_MB=0
 DEVICES=""
 EXCLUDE=""
 WORKER="/usr/local/lib/bee/bee-gpu-burn-worker"
@@ -68,8 +68,17 @@ trap 'rm -rf "${TMP_DIR}"' EXIT INT TERM
 WORKERS=""
 for id in $(echo "${FINAL}" | tr ',' ' '); do
     log="${TMP_DIR}/gpu-${id}.log"
-    echo "starting gpu ${id}"
-    "${WORKER}" --device "${id}" --seconds "${SECONDS}" --size-mb "${SIZE_MB}" >"${log}" 2>&1 &
+    gpu_size_mb="${SIZE_MB}"
+    if [ "${gpu_size_mb}" -le 0 ] 2>/dev/null; then
+        total_mb=$(nvidia-smi --id="${id}" --query-gpu=memory.total --format=csv,noheader,nounits 2>/dev/null | tr -d '[:space:]')
+        if [ -n "${total_mb}" ] && [ "${total_mb}" -gt 0 ] 2>/dev/null; then
+            gpu_size_mb=$(( total_mb * 95 / 100 ))
+        else
+            gpu_size_mb=512
+        fi
+    fi
+    echo "starting gpu ${id} size=${gpu_size_mb}MB"
+    "${WORKER}" --device "${id}" --seconds "${SECONDS}" --size-mb "${gpu_size_mb}" >"${log}" 2>&1 &
     pid=$!
     WORKERS="${WORKERS} ${pid}:${id}:${log}"
 done